From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Letter responding to Major Carter's query about running six-cylinder car engines without a damper.
| Identifier | ExFiles\Box 25\3\ Scan182 | |
| Date | 22th November 1926 | |
| 22. 11. 26 With reference to the question asked in Major Carter's letter, we regret we have no experience of running either of our six cylinder car engines for any considerable periods near the main synchronous speed without a damper. We have, however, record of running the 40/50 H.P. engine at 83% of the original synchronous speed continuously for 32 hours, and the 20 H.P. within 76% of this speed, for considerable periods without any signs of fatigue; but in each case our standard damper of the solid friction type was employed. The chief use of our damper is to damp out the lower harmonies, or the vibrations experienced at a half, a third and a quarter of the main synchronous speed when running without a damper, and which naturally come well within the working speed range. This the damper accomplishes successfully, but it does not prove effective in appreciably reducing the vibration amplitude at the synchronous speed, which, by the "feel" of the engine, is just as vigorous with as without the damper. If we appreciably increase the friction of the damper, we reduce the critical vibration, but the vibration at the half speed becomes manifest. For this reason the damper is adjusted to eliminate the vibrations which occur within our normal speed range. Therefore, during the time the engine was running at 83% of the synchronous speed, we do not think it would derive much benefit from the damper as then adjusted, and the condition would approximate to that existing without a damper. Major Carter will remember that our damper is a case of one having an infinitely rigid drive, being mounted directly on the end of the crankshaft. By increasing the damper friction, we do not reduce the synchronous speed but divide the vibration into two others - the one at the original synchronous speed of 3200 R.P.M., and the other at 2000 R.P.M. Increasing the damper friction results in a decrease of the previous synchronous vibration and growth of the one at 2000 R.P.M. This seems to possess the characteristic of the flexible drive damper, and we wonder if this is a peculiarity of the solid friction type, or is due to some other factor connected with the six cylinder crankshaft. We have enclosed a copy of a report on some experiments in connection with a friction mounted flywheel, which may be of interest. One point is that the vibration amplitude on the 40/50 H.P. crankshaft is much less than on the 20 H.P. - | ||